Mobil Corp. President William P. Tavoulareas, differing with both the Reagan administration and most oil industry executives, said today that the government should develop new standby rationing plans for gasoline and other types of petroleum fuels.

Addressing the company's annual meeting here, Tavoulareas also endorsed the idea of private financing for the nation's Strategic Petroleum Reserve through securities backed by the oil in storage. However, he said that oil companies, "which some say would have an interest in speculating in these certificates, should be declared ineligible to deal in these instruments."

The Mobil official praised the administration for promptly ending price controls on domestically produced crude oil and gasoline, but added, "We still need a long-term energy program. Decontrol, by itself, is not a comprehensive energy program."

Tavoulareas said it is only "realistic" to plan to deal "with possible oil shortage that might develop in the years ahead . . . although the United States has a comfortable margin of supply right now, we should not be complacent. . . . We . . . have to assume that there really can be an insufficient supply of oil to meet demand."

A rationing plan under which consumers were free to buy and sell rationing coupons -- a so-called white-market approach -- would be much preferable to either government allocation of supplies or the World War II-type of rationing in which coupons could not be sold legally, he said.

Energy Secretary James Edwards and other Reagan administration officials strongly oppose any form of rationing and do not plan to seek renewal of the present standby plan proposed by the Carter administration at congressional insistence. Authority for the present plan -- which energy officials say could take up to six months to put into effect after a shortage was declared -- expires at the end of September.

Many energy experts believe even a white-market rationing plan would prove administratively unworkable, partly because it would amount virtually to creation of a second currency.

A number of economists have proposed an alternative -- levying a tax on imported oil which would raise prices to oil users to balance supply and demand in the face of a major shortage. Edwards, who also opposes such a tax, believes the marketplace would achieve the same balancing of supply and demand. He has said there should be no government intervention unless an oil shortage is so severe that it threatens national security in a military sense.

A number of proposals involing private financing of filling the proposed 750-million-barrel petroleum reserve are pending in Congress. Most of them are intended to counter the high cost to the government of buying the oil it is now putting into salt dome caverns in Louisiana and Texas. The administration, which budgeted $3.9 billion for the SPR in fiscal 1982, considered -- but did not propose -- financing the reserve by issuing oil-backed bonds which would be sold to private investors. Officials at Treasury and the Council of Economic Advisers opposed such a plan.

In addition to setting up standby rationing and filling the SPR, the government should "encourage oil companies to join together in research and in some of the large, risky projects that will have to be set up to deal with the new energy sources," Tavoulareas said.